Currently, evaporation has been popular in the process for fabricating an organic light emitting diode (OLED). An evaporation apparatus generally has an inline type construction or a cluster type construction. A cluster type evaporation apparatus generally adopts a manipulator arm for conveying a glass substrate into respective chamber. After the substrate is aligned with a mask plate, the evaporation starts. In the inline type, the substrate is fastened on a conveying device. After alignment with the mask plate, the substrate is moved at a constant speed over heating sources in which different materials are filled, so that an OLED device is formed on the substrate.
As compared with the cluster type, the inline type evaporation apparatus has advantages of saving space and reducing tact time. However in the inline type design, it is a great challenge to carry and convey the substrate, align the substrate with the mask plate, and move to an evaporation chamber. Due to the weight and bending of the substrate with a large size, the substrate is generally conveyed in an upright posture. This requires that a linear heating source is also in the upright posture, which increases the difficulty in controlling the linear heating source to maintain thickness uniformity of the organic material in the evaporation process. Besides, in the upright conveying process, a film evaporating surface of the substrate is directed obliquely upwards, particles are prone to deposit on the film evaporating surface of the substrate, and this increases the defect rate due to particles and reduces yield.
To avoid the above problems, in the inline type design, a TFT face (i.e., the film evaporating surface) of the substrate is also directed downward during conveying in a large scale evaporation apparatus. To overcome factors like the weight and bending of the substrate with a large size, the substrate is generally fastened on the conveying device by electrostatic fastening or adhesive fastening. However, electrostatic fastening tends to cause damage to the TFT on the substrate. As for adhesive fastening, it is difficult to control the adhesion strength of the adhesive. Low adhesion strength leads to the substrate falling off, while high adhesion strength leads to difficulty in subsequent detaching. In addition, the adhesive will change its adhesion properties, or will age when it is heated during evaporation.